identifying cows; and 9) managerial ability and desire to make the system work.

Relative Merit of Breeds

Fig. 3 A crossbreeding system with a terminal sire breed (T) used with females produced from a two breed rotation of breeds A and B.

What are the relative merits of breeds of cattle available? This question is addressed by Cundiff in this volume.[3] Growth rate is important in having cattle reach market weights in a desirable length of time. However, more rapid growth is generally associated with increased mature size and the increased energy needed to sustain each animal. Consumers are continually demanding leaner and leaner meat products, but fat is important to the biological function of the beef cow. External fat serves as insulation and internal fat serves as reserve energy for continuing productive function in times of restricted energy availability. The age at which a female attains sexual maturity indicates her potential for reproduction. Overuse of late-maturing types will result in inadequate conception rates in yearling heifers. Adequate milking ability of the cow is necessary for her calf to express its genetic potential for

Fig. 2 A two breed rotation crossbreeding system imple mented with bulls of breeds A and B.

growth early in life. However, the cow must convert feed energy to milk and maintain the machinery required to produce the milk. Cows with high potential levels of milk production and large mature size need better nutritive environments than cows with lesser genetic potentials.

Some breeds are useful only at restricted levels. In northern environments, some restriction on the percentage of Bos indicus germplasm is prudent. Likewise, under warmer and more humid conditions some restriction on the percentage of Bos taurus germplasm is probably warranted. When heterosis effects are large relative to differences among breeds, there is less concern with using breeds in specialized roles and more with using a number of breeds in general-purpose roles. As breed differences become more important, using a particular breed characterized by high genetic potential for lean tissue growth rate in the role of a terminal sire becomes increasingly advantageous. When a terminal sire system is adopted, heterosis and maternal characteristics should be further emphasized in the cow herd.

Market Endpoint for Calves

If calves are sold at weaning, then heterosis is relatively more important and breed differences are of lesser importance. As ownership is retained to endpoints closer to the ultimate consumer, heterosis becomes relatively less important and breed differences are of increased importance. Calves also may be marketed to a middleman, and a premium may be received based on their anticipated future performance. Similarly, some producers will choose to participate in branded beef programs that specify breed composition. These marketing strategies effectively reduce the importance of heterosis and increase the importance of breed differences. However, heterosis still results in a 7% increase in the production of retail cuts per cow.

Far too many people struggle to fall pregnant and conceive a child naturally. This book looks at the reasons for infertility and how using a natural, holistic approach can greatly improve your chances of conceiving a child of your own without surgery and without drugs!